Those rebates will be available through March from the Kaua'i Island Utility Cooperative and the Hawaiian Electric Co.

They are a small initial step toward a recently-announced goal of entirely carbon-free transportation, with all ground vehicles running on renewable energy by 2045.

Hawaii already has a goal for utilities to generate 100 percent of electricity from renewable sources by that year, according to CBS News, and is now considering how to extend that provision to transportation.

This would require "vehicle-to-grid" technology that has been tested in the past by entities including the U.S. Air Force and the University of Delaware.

No automaker currently offers an electric car that can discharge power back into the grid, and utilities have yet to devise a mechanism for controlling the process and reimbursing customers.

Regardless, the renewable-energy mandate means whatever electric cars do end up on Hawaiian roads will have lower overall emissions than their counterparts charged from coal-fired grids on the mainland.

Because as a power source gets cleaner, so do the cars charged from it.